Customizing the LP Print Service

Although the LP print service is designed to be flexible enough to
handle most printers and printing needs, the LP print service does not
handle every possible situation. You might have a print request that is not
accommodated by the standard features of the LP print service. Or, you might
have a printer that does not quite fit into the way the LP
print service handles printers.

You can customize the LP print service in the following ways:

Adjust the printer port characteristics.

Adjust the terminfo database.

Customize the printer interface program.

Create a print filter.

Define a form.

Adjusting Printer Port Characteristics

The printer port characteristics set by the LP print service must be compatible
with the printer communication settings. If the default printer port settings provided by
the LP print service do not work with a printer, refer to the
printer manual from the manufacturer to determine what settings the printer requires from
the LP print service. Use the stty command to set and display printer
communication settings.

The following table shows the default stty settings that are used by the
LP print service.

Table 8-1 Default stty Settings Used by the LP Print Service

Option

Description

-9600

Sets baud to 9600

-cs8

Sets 8-bit bytes

-cstopb

Sends one stop bit per
byte

-parity

Does not generate parity

-ixon

Enables XON/XOFF (also known as START/STOP or DC1/DC3)

-opost

Does
“output post-processing” using all the settings that follow in this table

-olcuc

Do not map
lowercase to uppercase

-onlcr

Changes linefeed to carriage return/linefeed

-ocrnl

Does not change carriage returns into
linefeeds

-onocr

Outputs carriage returns even at column 0

-n10

Provides no delay after linefeeds

-cr0

Provides no
delay after carriage returns

-tab0

Provides no delay after tabs

-bs0

Provides no delay after backspace
characters

-vt0

Provides no delay after vertical tabs

-ff0

Provides no delay after form feeds

How to Adjust the Printer Port Characteristics

Become superuser.

Adjust the printer port characteristics.

# lpadmin -pprinter-name-o "stty=options"

-p

Specifies the name of the printer for which you are adjusting the port characteristics.

-o “stty=options”

Sets the port characteristic (stty option) specified by options. You can change more than one stty option setting with this command. Enclose each option in single quotation marks, and use a space to separate the options. For a complete list of options, see thestty(1) man page. Table 8-1 shows the default stty settings used by the LP print service.

Verify that the printer port characteristics have been changed.

# lpstat -pprinter-name-l

Example 8-1 Adjusting the Printer Port Characteristics

This example shows how to set the port characteristics for the printer
luna. The parenb option enables parity checking/generation. The parodd option sets odd parity
generation. The cs7 option sets the character size to 7 bits.

# lpadmin -p luna -o "stty='parenb parodd cs7'"

Example 8-2 Setting the Terminal Baud Rate

This example shows how to set the terminal baud rate to 19200
for the printer venus.

# lpadmin -p venus -o "stty=19200"

Adding a terminfo Entry for an Unsupported Printer

The LP print service uses an interface program and the terminfo database to
initialize each printer and establish the following:

Selected page size

Character pitch

Line pitch

Character set

Each printer is identified in the terminfo database with a short name. The
short name required by the terminfo database is identical to the name used
to set the TERM shell variable. This name is also the printer type
that you specify when setting up a printer. For example, the entries for
different types of PostScript printers are in the /usr/share/lib/terminfo/P directory. The default entries provided
with the SunOS software release are PS (for PostScript) and PSR (for PostScript
Reverse).

If you cannot find a terminfo entry for your printer, you still might
be able to use the printer with the LP print service without the
automatic selection of page size, pitch, and character sets. However, you might have
trouble keeping the printer set in the correct modes for each print request.

If no terminfo entry exists for your type of printer and you
want to keep the printer set in the correct modes, you can do
one of the following:

Customize the interface program used with the printer.

Add an entry to the terminfo database.

A terminal or printer entry in the terminfo database contains and defines hundreds
of items. The LP print service, however, uses fewer than 50 of these
items. For more information about the terminfo items that are required for a
printer, see Required terminfo Items For a Printer.

How to Add a terminfo Entry for an Unsupported Printer

Note - Before you create a terminfo entry for a printer, make sure that none
of the existing terminfo entries will support the printer. To do so, try
to set up the printer with an entry for a similar printer, if
a similar printer exists.

The directories in the /usr/share/lib/terminfo directory contain all the valid terminfo entries. Use
these entries as a guide for choosing a name for the printer.

Create a terminfo entry file for the printer.

Table 13-6 shows the items you must define in the terminfo entry to add
a new printer to the LP print service. For more details about
the structure of the terminfo database, see the terminfo(4) man page.

To help you start writing a new terminfo entry, use the infocmp command
to save an existing terminfo entry to a file. This command is
helpful if there is a terminfo entry that is similar to entry
you want to create. For example, the following command saves the ps entry
to the ps_cust file, which will become the new terminfo entry.

infocmp ps > ps_cust

Compile the terminfo entry file into the terminfo database.

# ticterminfo_entry

where terminfo-entry variable is the terminfo entry file you created.

Check for the new terminfo entry file in the /usr/share/lib/terminfo directory.

Customizing the Printer Interface Program

If you have a printer that is not supported by the standard
printer interface program, you can furnish your own printer interface program. You can copy
the standard program and then tell the LP print service to use
it for a specified printer. First, you need to understand what is in
the standard program. The following section describes the standard program.

A printer interface program should perform the following tasks:

Initialize the printer port, if necessary. The standard printer interface program uses the stty command to initialize the printer port.

Initialize the printer hardware. The standard printer interface program receives the control sequences from the terminfo database and the TERM shell variable.

Print a banner page, if necessary.

Print the number of copies that are specified by the print request.

Caution - If you have a printer interface program from a release of UNIX System
V prior to release 3.2, it will probably work with the SunOS
5.10 or compatible LP print service. However, several -o options have been standardized in
the SunOS 5.10 or compatible LP print service. These options are passed to
every printer interface program. These options might interfere with similarly named options used
by the old interface.

The LP print service, not a printer interface program, is responsible for opening
the printer port. The printer port is given to the printer interface program
as standard output. In addition, the printer is identified as the “controlling terminal”
for the printer interface program so that a “hang-up” of the port causes
a SIGHUP signal to be sent to the printer interface program.

Standard Printer Interface Program

The standard (model) printer interface program is /usr/lib/lp/model/standard. This program is used
by the LP print service to set the printing defaults shown in the
following table.

Exit Codes

When printing is complete, your interface program should exit with a code that
shows the status of the print job. The exit code is the
last entry in the printer interface program.

The following table shows the exit codes and how they are interpreted by
the LP print service.

Table 8-3 Printer Interface Program Exit Codes

Exit Code

Meaning to the LP Print Service

0

The print
request has been successfully completed. If a printer fault occurred, it has been
cleared.

1 to 127

A problem was encountered when printing a request. For example,
there were too many nonprintable characters or the request exceeds the printer's capabilities. The
LP print service notifies the person who submitted the request that an error
occurred when printing it. This error does not affect future print requests. If
a printer fault has occurred, it has been cleared.

128

This code is reserved
for use by the LP print service. Interface programs must not exit with
this code.

129

A printer fault was encountered when printing the request. This fault does
affect future print requests. If the fault recovery for the printer directs the
LP print service to wait for the administrator to correct the problem, the
LP print service disables the printer. If the fault recovery is to
continue printing, the LP print service does not disable the printer. However, the print
service will try printing again in a few minutes.

>129

These codes are reserved
for use by the LP print service. Interface programs must not exit with
codes in this range.

If the program exits with a code of 129, root is alerted of
a printer fault. The LP print service must also reprint the request from
the beginning, after the fault has been cleared. If you do not
want the entire request to be reprinted, you can have the interface program
send a fault message to the LP print service. (First wait for the
fault to be cleared.) When the fault is cleared, the interface program can
resume printing the file. When printing is finished, the printer interface program can
give a 0 exit code, just as if the fault had never occurred.
An added advantage of this approach: The interface program can detect when the
fault is cleared automatically. Thus, the administrator does not need to re-enable the
printer.

Fault Messages

You can use the lp.tell program to send fault messages to the LP
print service. This program is referenced by the LPTELL shell variable in the
standard printer interface code. The program takes standard input and sends it to
the LP print service. The LP print service puts standard input into the
message that alerts the administrator to the printer fault. If its standard input
is empty, the lp.tell program does not initiate an alert. For an example
of how the lp.tell program is used, examine the standard printer interface code
immediately after the following comment:

# Set up the $LPTELL program to capture fault messages here

If you use the special exit code 129 or the lp.tell program,
the printer interface program does not need to disable the printer itself. The
interface program can disable the printer directly. However, doing so overrides the fault-alerting
mechanism. Alerts are sent only if the LP print service detects that the
printer has a fault, and the special exit code and the lp.tell program
are its main detection tools.

If the LP print service has to interrupt printing of a file
at any time, it kills the interface program with a signal TERM (trap
number 15). For more information, see the kill(1) and signal(3C) man pages. If
the printer interface program dies from receipt of any other signal, the LP
print service assumes that future print requests are not be affected. As a
result, the LP print service continues to use the printer. The LP print
service notifies the user who submitted the request that the request has not
been finished successfully.

When the interface is first invoked, the signals HUP, INT, QUIT, and PIPE
(trap numbers 1, 2, 3, and 13) are ignored. The standard interface
changes this default behavior, so that the signals are trapped at appropriate times. The
standard interface interprets receipt of these signals as warnings that the printer has
a problem. When the standard interface receives a signal, it issues a fault
alert.

Using a Customized Printer Interface Program

You can create a customized printer interface program and use it instead of
the standard printer interface program on the print server. To do so,
you use the lpadmin command to register the program with the LP print service
for a specific printer.

How to Set Up a Custom Printer Interface Program

Become superuser.

Copy the standard printer interface program.

# cp /var/spool/lp/model/standardcustom-interface

(Optional) If you already have a custom printer interface program, go to Step 5.

Change the copy of the standard printer interface program to meet your needs.